Bi-Metallic Component And Method Of Making The Same

ABSTRACT

In one aspect, the invention is directed to a half-cradle for use in a vehicle frame, comprising a cast end member formed from a first material and first and second tubular cross-member stubs extending from the cast end member. The first and second tubular cross-member stubs are made from a second material. Each of the stubs has an end buried in the cast end member, wherein the buried end is uncapped. Each of the tubular cross-member stubs has an interior that is configured to sealingly receive a core for use in preventing the filling of the stub with molten first material during casting of the cast end member.

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. National Stage patent application claims priority toInternational Patent Application Serial No. PCT/CA2011/000060 filed onJan. 20, 2011, entitled “Bi-Metallic Component And Method Of Making TheSame” and U.S. Provisional patent application No. 61/296,727 filed onJan. 20, 2010, the entire disclosures of all of these applications beingconsidered part of the disclosure of this application and are herebyincorporated by reference.

FIELD OF THE INVENTION

The instant invention relates generally to components for use inautomotive applications, such as for instance automotive engine cradles,frames and suspensions, or to components for use in non-automotiveapplications, and more particularly to bi-metallic components that areformed by joining together at least two parts that are fabricated fromdifferent materials, such as for instance steel and aluminum.

BACKGROUND OF THE INVENTION

A wide variety of components for automotive and non-automotiveapplications are now being fabricated using a process in which one partis cast around a portion of another part. In some cases, the differentparts of the component are fabricated using different materials, so asto provide a finished component with desired weight and/or strengthcharacteristics. By way of a few specific and non-limiting examples, anengine cradle is formed by casting aluminium end members around the endsof hollow, steel cross-members, or a torsion beam axle assembly isformed by casting an aluminium trailing arm around an end portion of asteel torsion beam, as described for instance in U.S. Pat. No. 7,837,230and U.S. patent application Ser. No. 12/911,930.

A typical process for manufacturing an engine cradle includes coveringthe open ends of each of the hollow, steel cross-members with an endcap. The covered ends of the steel cross-members are then introducedinto a mold of predetermined shape and are held in place. Moltenaluminum is introduced into the mold at relatively high pressure and iscooled, so as to cast an end member around the ends of each of thecross-members. The purpose of the end caps primarily is to prevent themolten aluminum from entering and filling the cross-member during thecasting process. In order to ensure that the molten aluminum does notenter the hollow cross-member during the casting process, typically theentire length of the mating seam between the end cap and thecross-member is welded. Once the casting step has taken place, an X-rayscan of the casting is carried out in order to verify whether there areany defects in the castings.

Of course, the end caps that are used to cover the ends of thecross-members add weight to the cradle, which results in higher unitcosts and leads to lower fuel efficiency in the finished automobile.Further, the end caps are sometimes deformed under the influence of thehigh pressure that is exerted during the casting process. Further still,the presence of the end caps can create air pockets during an e-coatingstep, and it may be relatively difficult to drain the excess e-coat fromthe cross-members since the ends of the cross-members necessarily haveno holes.

Another disadvantage of this process is that the ends of thecross-members typically are formed into a cylindrical shape, and theyare covered using circularly shaped end caps in order to create apressure vessel that is able to withstand the pressure exerted by themolten aluminum in the mold. Of course, a cylindrical shape is notnecessarily an optimal shape for supporting a load during use.

Additionally, transporting, handling and storing of completed cradlescan be cumbersome because of the weight of the completed cradle and alsobecause of its size. Often, specialized equipment is required duringhandling and transporting of the completed cradles. Furthermore, thecompleted cradles occupy a relatively large amount of space even thougheach cradle has a large amount of empty space associated therewith. Ofcourse, in the event that an X-ray scan reveals a defect in one of thetwo castings in a finished cradle, it is necessary to scrap the entirecradle even if the other casting in the cradle has no defects. This canresult in a scrap rate for cradles as high as 10% in some cases.

Other components may be manufactured in a similar way, such as forinstance torsion beam axle assemblies, control arms, etc. For instance,each end of a steel torsion beam is covered with an end cap as describedabove, and each end of the torsion beam is introduced into a mold.Molten aluminum is introduced into each mold at relatively high pressureand is cooled, so that a trailing arm is cast around the each end of thetorsion beam. Torsion beams, or control arms, that are formed in thismanner also suffer the above-noted disadvantages.

In WO 2008/004715, Ko proposes an alternative arrangement for a torsionbeam axle. In particular, the torsion beam axle includes a torsion beam,a plurality of trailing arms made from a material different than that ofthe torsion beam, and connecting tubes made of a material better thanthat of the trailing arms with respect to weldability with the torsionbeam, the connecting tubes integrally coupled with the trailing arms atone end thereof. Unfortunately, Ko merely provides a schematicillustration of a finished torsion beam axle assembly in cross-sectionalview, in which the material of the trailing arm surrounds the one end ofthe connecting tube and extends through anchoring-slots at the one endof the connecting tube. In this rather fanciful disclosure, Ko neithersuggests a suitable process for fabricating the finished torsion beamaxle, nor does Ko even appear to contemplate the difficulties that areassociated with casting the trailing arm around the one end of thehollow connecting tube. As such, it appears that Ko intended for it tobe left entirely to the reader to devise a suitable process for formingthe torsion beam axle assembly. Such a process must prevent moltenmaterial, which is used to form the trailing arm, from being ejectedunder pressure from the mold via the hollow connecting tube. Inaddition, such a process must also prevent filling of the connectingtube by the solidified trailing arm material in the finished product. Ofcourse, this leaves it to the reader to solve a significant problem,requiring simultaneous consideration of complex engineering issues aswell as safety issues, manufacturing process issues and economic issues.

It would therefore be desirable to provide a bi-metallic component, suchas for instance an engine cradle, a torsion beam axle assembly or acontrol arm, and a process for manufacturing the same, which overcomesat least some of the above-noted disadvantages.

SUMMARY OF EMBODIMENTS OF THE INVENTION

In one aspect, the invention is directed to a bi-metallic joint made upof a first member and a second member. The first member is cast aroundat least a portion of the second member. The first member is made from afirst material, such as for instance aluminum, magnesium, zinc, etc., oralloys thereof. The second member is made from a second material, suchas for instance steel, aluminum, copper, stainless steel, etc., oralloys thereof. The melting temperature of the first material is lowerthan, or may even be approximately equal to, the melting temperature ofthe second material, thereby permitting the first member to be castaround the second member.

To form the bi-metallic joint, a portion (e.g., an end) of the secondmember is positioned in a mold and held in place. Molten first materialis introduced into the mold and is solidified around the portion of thesecond member in the mold. In embodiments wherein the second member istubular, it may be provided with an end cap at the end that is in themold to prevent molten first material from escaping from the moldthrough the end of the second member. In some embodiments, wherein anend cap is provided, the portion of the second member in the mold andthe end cap may be configured to withstand the pressures of the moltenfirst material in the mold. Alternatively, the end cap and the portionof the second member in the mold may not be configured to withstand thepressures in the mold by themselves. Instead a removable core member maybe inserted into the interior of the second member and abutted with theend cap so that the core supports the second member and the end cap. Inthis way, the core prevents deformation of the second member and of theend cap, or at least prevents significant deformation of the secondmember and of the end cap. In some embodiments, the end cap is omittedentirely and a core is inserted into the interior of the second memberboth to support the second member and to seal against the escape ofmolten first material from the mold through the end of the secondmember. The core optionally extends into the mold farther than thesecond member, or is flush with the end of the second member, or thesecond member extends into the mold farther then the core.

The second member may be a stub member that is intended to be connectedto another member. For example, a cradle may be provided with one ormore second members that are stubs that are partially embedded in a castend member (as shown in FIG. 2). Cross-members, which are made from acompatible material to the stubs, can then be welded to the stubs. Forgreater certainty, in embodiments wherein a cast first member has aplurality of second members partially embedded therein, it is notnecessary that all the second members be made from the same material.

Preferably, the second member has features thereon that prevent slippagebetween the first and second members during use of the joint. Forexample, the second member may be generally rectangular incross-sectional shape (as shown in FIG. 2) to prevent rotation of thefirst member and second member relative to each other about an axisalong the length of the second member. Alternatively, the second membermay have a closed profile in cross section that is hexagonal, octagonal,L-shaped etc., to prevent rotation of the first member and second memberrelative to each other about an axis along the length of the secondmember. As another example, the second member may have a flange portionthereon to prevent the first and second members from being pulled apartby forces acting on the bi-metallic joint and to prevent rotation of thefirst and second members relative to one another. Alternatively, thesecond member may have slots or holes, either with or without hangingflaps of the second material, defined proximate the end of the secondmember that is positioned in the mold. The molten first material flowsthrough the slots or holes, thereby forming an anchoring andanti-rotation feature when the first material cools and solidifies.

The bi-metallic joint may be used in a number of applications, such ason a torsion beam axle assembly wherein the trailing arm is a firstmaterial such as cast aluminum and the torsion beam is a second materialsuch as steel, or on a cradle, such as a rear suspension cradle or anengine cradle wherein the end members are made from cast aluminum andany cross-beams are made from a first material, such as steel. Otherapplications include use of the bi-metallic joint in an instrument panelsupport structure, in a bumper assembly and in a control arm.

According to an aspect of an embodiment of the instant invention, thereis provided a bi-metallic component, comprising: a cast member formedfrom a first material; and a tubular stub member formed from a secondmaterial and having an open first end and an open second end that isopposite the first end, the cast member cast around the second end, andthe first end extending from the cast member, the stub member having aninterior surface that is configured to sealingly receive a removablecore member for preventing molten first material from flowing throughthe stub member between the second end and the first end thereof duringcasting of the cast member around the second end.

According to an aspect of another embodiment of the instant invention,there is provided a half cradle for use in a cradle in a vehicle frame,comprising: a cast end member formed from a first material; and firstand second tubular cross-member stubs, each formed from a secondmaterial and each having a first end and a second end that is oppositethe first end, the cast member cast around the second end of each of thefirst and second tubular cross-member stubs, and the first end of eachof the first and second tubular cross-member stubs extending from thecast member, each of the first and second tubular cross-member stubshaving an interior surface that is configured to sealingly receive aremovable core member for preventing molten first material from flowingthrough either one of the first and second tubular cross-member stubsbetween a respective second end and a respective first end thereofduring casting of the cast member.

According to an aspect of another embodiment of the instant invention,there is provided a torsion beam axle assembly, comprising: a casttrailing arm formed from a first material; and a torsion beam stubformed from a second material and having a first end and a second endthat is opposite the first end, the cast trailing arm cast around thesecond end of the torsion beam stub and the first end of the torsionbeam stub extending from the cast member, the torsion beam stub havingan interior surface that is configured to sealingly receive a removablecore member for preventing molten first material from flowing throughthe torsion beam stub between the second end and the first end thereofduring casting of the cast trailing arm around the second end.

According to an aspect of another embodiment of the instant invention,there is provided a control arm, comprising: a cast coupling memberformed from a first material; and a tubular stub member formed from asecond material and having a first end and a second end that is oppositethe first end, the cast coupling member cast around the second end ofthe tubular stub member and the first end of the tubular stub memberextending from the cast coupling member, the tubular stub member havingan interior surface that is configured to sealingly receive a removablecore member for preventing molten first material from flowing throughthe tubular stub member between the second end and the first end thereofduring casting of the cast coupling member around the second end.

According to an aspect of another embodiment of the instant invention,there is provided a full cradle for use in a vehicle frame, comprising:first and second half-cradles, each one of the first and secondhalf-cradles comprising: a cast end member formed from a first material;and, first and second tubular cross-member stubs formed from a secondmaterial, each of the first and second tubular cross-member stubs havingan open first end and an open second end that is opposite the first end,the cast end member cast around the second end of each of the first andsecond tubular cross-member stubs and the first end of each of the firstand second tubular cross-member stubs extending from the cast endmember, each one of the first and second tubular cross-member stubshaving an interior surface that is configured to sealingly receive aremovable core member for preventing molten first material from flowingthrough either one of the first and second tubular cross-member stubsbetween the respective second end and the respective first end thereofduring casting of the cast end member around the second end of each ofthe first and second tubular cross-member stubs; and, a firstcross-member connected between the first tubular cross-member stubs onthe first and second half-cradles, and a second cross-member connectedbetween the second tubular cross-member stubs on the first and secondhalf-cradles, wherein the first and second cross-members are made from amaterial that is weldable to the second material.

According to an aspect of another embodiment of the instant invention,there is provided a method of making a bi-metallic component,comprising: a) providing a first material; b) providing a tubular stubmember made from a second material; c) positioning a portion of thetubular stub member in a mold; d) removably inserting a core into thetubular stub member; e) introducing the first material in molten forminto the mold around the tubular stub member; f) holding the core in thetubular stub member with a sufficient force to prevent first materialfrom filling the tubular stub member; g) solidifying the first materialto form a cast member in the mold around a portion of the tubular stubmember, the solidified cast member and the tubular stub member togetherforming the bi-metallic component; and h) opening the mold to releasethe bi-metallic component.

According to an aspect of another embodiment of the instant invention,there is provided a method of making a half-cradle for use in a cradlein a vehicle frame, comprising: a) providing a first material; b)providing first and second tubular cross-member stubs made from a secondmaterial; c) positioning a portion of each of the first and secondtubular cross-member stubs in a mold; d) removably inserting first andsecond cores into the first and second tubular cross-member stubs,respectively; e) introducing the first material in molten form into themold around the first and second tubular cross-member stubs; f) holdingthe first and second cores in the first and second tubular cross-memberstubs with a sufficient force to prevent first material from filling thefirst and second tubular cross-member stubs; g) solidifying the firstmaterial to form an end member in the mold around the portion of each ofthe first and second tubular cross-member stubs, the solidified endmember and the first and second tubular cross-member stubs togetherforming a half-cradle; and h) opening the mold to release thehalf-cradle.

According to an aspect of another embodiment of the instant invention,there is provided a method of making a full cradle for use in a vehicleframe, comprising: a) making a first half-cradle according to the methoddescribed in the previous paragraph; b) making a second half-cradleaccording to the method described in the previous paragraph; c)connecting a first cross-member to the first tubular cross-member stubon each of the first and second half-cradles; and d) connecting a secondcross-member to the second tubular cross-member stub on each of thefirst and second half-cradles.

According to an aspect of another embodiment of the instant invention,there is provided a method of making a bi-metallic joint, comprising: a)providing a first metal; b) providing a second member made from a secondmetal, the second member having an end aperture at an end thereof; c)sealing the end aperture with an end cap; d) inserting a core into thesecond member in abutment with the end and with the end cap; e)positioning the end of the second member in a mold; f) introducing thefirst metal in molten form into the mold around the end of the secondmember and the end cap; g) solidifying the first metal to form a firstmember in the mold around the end of the second member and the end cap;and, h) removing the core from the second member, wherein the end capand the end of the second member are not sufficiently strong towithstand a pressure in the mold during steps f) and g), and, whereinthe core remains in abutment with the end and with the end cap duringsteps f) and g) and prevents substantial deformation of either the endor the end cap during steps f) and g).

According to an aspect of another embodiment of the instant invention,there is provided a method of making a bi-metallic joint, comprising: a)providing a first metal; b) providing a second member made from a secondmetal, the second member having an end aperture at an end thereof; c)removably inserting a core into the second member through an open firstend thereof, the core configured for substantially forming a seal,during a molding process, between an outer surface thereof and aninterior surface of the second member that faces the outer surface ofthe core; d) positioning an open second end of the second member in amold, the second open end opposite the first open end; e) introducingthe first metal in molten form into the mold around the second open endof the second member; f) solidifying the first metal to form a firstmember in the mold around the second open end of the second member; and,g) removing the core from the second member.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example only withreference to the attached drawings, wherein similar reference numeralsdenote similar elements throughout the several views, in which:

FIG. 1 is a perspective view of a cradle for use in a vehicle frame, inaccordance with an embodiment of the instant invention;

FIG. 2 is a perspective view of a half-cradle that is used in the cradleshown in FIG. 1;

FIG. 3 a is a cross-sectional view illustrating the casting of an endmember around two cross-member stubs, each of the cross-member stubsbeing shown with one end held in a mold and prior to receiving a core;

FIG. 3 b is a cross-sectional view illustrating the casting of an endmember around two cross-member stubs, each of the cross-member stubsbeing shown with one end held in a mold and with a core sealinglyreceived therein;

FIG. 3 c is a cross-sectional view illustrating the casting of an endmember around two cross-member stubs, each of the cross-member stubsbeing shown with one end held in a mold and with a core sealinglyreceived therein, and the mold cavity filled with the end-membermaterial in molten form;

FIG. 3 d is an enlarged cross-sectional view showing a slip-fitclearance “d” between the outer surface of the core and the innersurface of the cross-member stub prior to closing a mold, in anembodiment having core-associated and stub-associated sealing shoulders;

FIG. 3 e is an enlarged cross-sectional view showing a friction-fitbetween the outer surface of the core and the inner surface of thecross-member stub subsequent to closing the mold, in the embodimenthaving core-associated and stub-associated sealing shoulders;

FIG. 3 f is an enlarged cross-sectional view showing a slip-fitclearance “d” between the outer surface of a core and the inner surfaceof a cross-member stub prior to closing a mold, in an embodiment absentcore-associated and stub-associated sealing shoulders;

FIG. 3 g is an enlarged cross-sectional view showing a friction-fitbetween the outer surface of the core and the inner surface of thecross-member stub subsequent to closing the mold, in the embodimentabsent core-associated and stub-associated sealing shoulders;

FIG. 4 a is a cross-sectional view showing an optional end-feature atone end of a cross-member stub;

FIG. 4 b is a cross-sectional view showing another optional end-featureat one end of a cross-member stub;

FIG. 4 c is a cross-sectional view showing another optional end-featureat one end of a cross-member stub;

FIG. 4 d is a cross-sectional view showing another optional end-featureat one end of a cross-member stub;

FIG. 5 shows an exploded perspective view of the cradle shown in FIG. 1;

FIG. 6 is a perspective view of a torsion beam axle assembly accordingto an embodiment of the instant invention;

FIG. 7 is a perspective view of a control arm according to an embodimentof the instant invention; and

FIG. 8 is a cross-sectional view showing a bi-metallic joint accordingto an aspect of the instant invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable a person skilled in theart to make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe disclosed embodiments will be readily apparent to those skilled inthe art, and the general principles defined herein may be applied toother embodiments and applications without departing from the scope ofthe invention. Thus, the present invention is not intended to be limitedto the embodiments disclosed, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein. Anyreference in this disclosure to a metal will be understood to encompassboth the pure metal and alloys of the metal. For example, references toaluminum are intended to include both pure aluminum and aluminum alloys.

Reference is made to FIG. 1, which shows a cradle 10 for use in avehicle frame in accordance with an embodiment of the instant invention.The cradle 10 includes first and second half-cradles, which are shownindividually at 12 a and 12 b, respectively, and first and secondcross-members, which are shown individually at 14 a and 14 b,respectively. The cradle 10 may further include lower reinforcement bars(not shown).

Referring now to FIG. 2, shown is one of the half-cradles 12 a of thecradle 10 of FIG. 1. The half-cradle 12 a comprises an end member 18that is made from a first material, such as for instance aluminum or analuminum alloy, and first and second cross-member stubs, which are shownindividually at 20 a and 20 b, respectively. The first and secondcross-member stubs 20 a and 20 b are made from a second material havinga melting temperature that is higher than or approximately equal to themelting temperature of the first material, such as for instance steel.Each of the stubs 20 a and 20 b is tubular and defines an interiorsurface 21 a and 21 b, respectively. As is shown in accordance with thisembodiment, the stub 20 a is of rectangular cross section and 20 b is ofcircular cross section. Alternatively, other cross-sectional shapes maybe employed such as for instance square, oval, hexagonal, octagonal,other polygonal, L-shaped, etc. The stubs 20 a and 20 b provide aconnection surface or connection edge for connecting (e.g., bymechanical, chemical or fusion joint, including welding, riveting,bolting etc.) the cross-members 14 a and 14 b of FIG. 1. When connectingis achieved by welding, the cross-members 14 a and 14 b are made from acompatible material (e.g., a material that is weldable to the secondmaterial). In one embodiment, the cross-members 14 a and 14 b are madefrom the same material that is used to make the stubs 20 a and 20 b,such as for instance steel.

The half-cradle 12 a, and similarly the half cradle 12 b, can bemanufactured without the need for end caps on the cross-member stubs 20a and 20 b. To manufacture the half-cradle 12 a, and similarly the halfcradle 12 b, the cross-member stubs 20 a and 20 b are introduced into amold 22, as shown in greater detail in FIG. 3 a, such that a respectivefirst end 24 a and 24 b of the stubs 20 a and 20 b extends into a moldcavity 26 of the mold 22. More specifically, when the mold 22 is openthe stubs 20 a and 20 b are positioned on one of the mold plates. Themold 22 is then closed, and the stubs 20 a and 20 b are held in placewith their respective first ends 24 a and 24 b extending into the moldcavity 26.

Referring also to FIG. 3 b, a first core 28 a is inserted into the firststub 20 a and a second core 28 b is inserted into the second stub 20 b,such that a sealing shoulder (core-associated sealing shoulder, e.g.,item 30 b in the inset) that is defined along an exterior surface of thecores 28 a and 28 b sealingly engages a sealing shoulder(stub-associated sealing shoulder, e.g., item 32 b in the inset) definedalong the interior surface of the first and second stubs 20 a and 20 b.

Referring now to FIG. 3 b and FIG. 3 c, with the first and second cores28 a and 28 b in place the molten first material 33 (e.g., moltenaluminum or aluminum alloy) is introduced into the mold cavity 26. Inthe case of a semi-automated or fully-automated application, a force isprovided such as by using a not illustrated hydraulic ram for urging thecore 28 a and 28 b against the sealing shoulder on the first and secondstubs 20 a and 20 b, respectively. While the force is being applied tothe cores 28 a and 28 b, the molten first material 33 is prevented fromescaping through the space between the core 28 a and 28 b and the firstand second stubs 20 a and 20 b. Alternatively, in a manual applicationthe cores 28 a and 28 b and the first and second stubs 20 a and 20 b areheld in place by a backing part that is associated with the mold 22. Inother words, when the first material 33 is introduced into the moldcavity 26 under pressure, the cores 28 a and 28 b and the first andsecond stubs 20 a and 20 b are pressed against the backing part, suchthat they are substantially prevented from moving. It will be noted thatthe fluid pressure of the first material 33 in the mold cavity 26 can berelatively high in order to thoroughly pack the mold cavity 26, however,the presence of the cores 28 a and 28 b prevents the ends 24 a and 24 bof the stubs 20 a and 20 b from collapsing. The cores 28 a and 28 b maythemselves be solid (i.e., not hollow), at least within a portionthereof that supports the ends 24 a and 24 b, so as to help support theends 24 a and 24 b of the stubs 20 a and 20 b, respectively, againstcollapse.

As is shown in FIGS. 3 b and 3 c, the cores 28 a and 28 b include afeature proximate the end 34 a and 34 b, respectively, which allows someof the molten first material 33 to support the inside of the stubs 20 aand 20 b, respectively. In this way, the first material 33 is castaround the inner and outer surfaces of the ends 24 a and 24 b of thestubs 20 a and 20 b, respectively.

Referring now to FIG. 3 d, shown is an enlarged cross-sectional viewshowing the cross-member stub 20 a located between an upper die 22 a anda lower die 22 b of the mold 22, with the core 28 a inserted in placewithin the cross-member stub 20 a. There is a slip-fit clearance “d”between the outer surface of the core 28 a and the inner surface of thecross-member stub 20 a prior to closing the mold 22, as shown in theinset. The slip-fit clearance “d” enables insertion of the core 28 ainto the cross-member stub 20 a. A circumferential flange 38 is providedaround one end of the core 28 a for locating the core 28 a within thecross-member stub 20 a. Further, in this specific and non-limitingexample the lower die 22 b includes a backing part for retaining thecore 28 a and cross-member stub 20 a when the molten first material isintroduced into the mold under high pressure. Similarly, thecross-member stub 20 b includes a circumferential flange for locatingthe core 28 b within the cross-member stub 20 b. Also similarly, thecore 28 b and the cross-member stub 20 b are retained during the castingprocess due to the presence of a backing part of the lower die 22 b,which is located proximate the end of the core 28 b and cross-memberstub 20 b that protrudes from the mold 22.

Referring now to FIG. 3 e, when the mold 22 is closed the ductility ofthe material that is used to form the cross-member stub 20 a allows theend 24 a to deform slightly, such that an interference fit is createdbetween the end 24 a of the cross-member stub 20 a and the core 28 a.The resulting interference fit substantially prevents molten firstmaterial 33 from being ejected from the mold cavity 26 through the spacebetween the outer surface of the core 28 a and the inner surface of thecross-member stub 20 a. Of course, an interference fit is createdbetween the cross-member stub 20 b and the core 28 b in substantiallythe same way. The feature proximate the end 34 a of the core 28 a allowsmolten first material to support the inner side of the cross-member stub20 a, such that in the finished bi-metallic joint the first materialsurrounds the end 24 a of the cross-member stub 20 a, including theoptional flange feature 36. When slots or holes are provided through thewall material proximate the end 24 a of the cross-member stub 20 a, thefeature proximate the end 34 a of the core 28 a allows the molten firstmaterial to flow around the inner and outer surface of the end 24 a ofthe cross-member stub 20 a and through the provided slots or holesbetween the inner and outer surfaces.

Referring now to FIG. 3 f, shown is an enlarged cross-sectional viewshowing the cross-member stub 20 a located between an upper die 22 a anda lower die 22 b of the mold 22, with the core 28 a inserted in placewithin the cross-member stub 20 a. FIG. 3 f illustrates an optionalembodiment in which the core-associated and stub-associated sealingshoulders are absent. There is a slip-fit clearance “d” between theouter surface of the core 28 a and the inner surface of the cross-memberstub 20 a prior to closing the mold 22. The slip-fit clearance “d”enables insertion of the core 28 a into the cross-member stub 20 a. Acircumferential flange 38 is provided around one end of the core 28 afor locating the core 28 a within the cross-member stub 20 a. Further,in this specific and non-limiting example the lower die 22 b includes abacking part for retaining the core 28 a and cross-member stub 20 a whenthe molten first material is introduced into the mold under highpressure. Similarly, the cross-member stub 20 b includes acircumferential flange for locating the core 28 b within thecross-member stub 20 b. Also similarly, the core 28 b and thecross-member stub 20 b are retained during the casting process due tothe presence of a backing part of the lower die 22 b, which is locatedproximate the end of the core 28 b and cross-member stub 20 b thatprotrudes from the mold 22.

Referring now to FIG. 3 g, when the mold is closed the ductility of thematerial that is used to form the cross-member stub 20 a allows the endthereof to deform slightly, such that an interference fit is createdbetween the end of the cross-member stub 20 a and the core 28 a. Theresulting interference fit substantially prevents molten first material33 from being ejected from the mold cavity 26 through the space betweenthe outer surface of the core and the inner surface of the cross-memberstub, even though the core-associated and stub-associated sealingshoulders are absent. Of course, an interference fit is created betweenthe cross-member stub 20 b and the core 28 b in substantially the sameway. The feature proximate the end 34 a of the core 28 a allows moltenfirst material to support the inner side of the cross-member stub 20 a,such that in the finished bi-metallic joint the first material surroundsthe end 24 a of the cross-member stub 20 a, including the optionalflange feature 36. When slots or holes are provided through the end 24 aof the cross-member stub 20 a, the feature proximate the end 34 a of thecore 28 a allows the molten first material to flow around the inner andouter surface of the end 24 a of the cross-member stub 20 a and throughthe provided slots or holes between the inner and outer surfaces.

Referring again to FIG. 3 c, after the mold cavity 26 is sufficientlypacked with the first material the mold cavity 26 is cooled in order tosolidify the first material and thereby form the end member 18 aroundthe ends 24 a and 24 b of the stubs 20 a and 20 b, respectively. Oncethe end member 18 is solidified, the cores 28 a and 28 b are removedfrom the stubs 20 a and 20 b and the mold 22 is opened, so as to releasethe half-cradle 12 a. Optionally, the cores 28 a and 28 b are coatedwith a suitable coating that facilitates their removal from thesolidified first material.

As is shown in FIG. 3 c, the cores 28 a and 28 b have an end 34 a and 34b, respectively, that may optionally extend beyond the ends 24 a and 24b of the stubs 20 a and 20 b, respectively, into the mold cavity 26. Asa result, the cores 28 a and 28 b create hollow portions in the endmember 18 that would otherwise be filled with first material 33, whichmakes for a lighter half-cradle 12 a than would otherwise be createdwith a core that did not extend into the mold cavity beyond the end ofthe stubs 20 a and 20 b.

Because the cores 28 a and 28 b occupy the interior volumes of the stubs20 a and 20 b, respectively, the stubs 20 a and 20 b are prevented fromcollapsing inwardly under the influence of the pressure of the moltenfirst material 33 in the mold cavity 26. As a result, the stubs 20 a and20 b do not need to have a shape that is particularly suited toinhibiting collapse, and can instead have a shape that is suited toresist the stresses that will be incurred during its use in the vehicle.For example, the stub 20 a may have a rectangular shape, wherein thestub 20 a has a height that is larger than its width. Alternatively, thestubs 20 a and/or 20 b are formed with a different cross-sectional shapesuch as for instance the shape of a hexagon, an octagon, anotherpolygon, an oval, or an L-shape, etc. As a result, in the instantexample the stub 20 a can be joined with the cross-member 14 a, whichhas a similar rectangular shape, and also has a height that is largerthan its width. The shape of the stub 20 a and cross-member 14 a (havinga height larger than the width) makes them particularly suited to resistvertically oriented loads while maintaining relatively low weight. Bycontrast, the ends of cross-members used in cradles of the prior art aretypically cylindrical so as to make them resistant to collapse duringmanufacturing, which unfortunately restricts the capability to configurethem to resist the stresses incurred during their use in the vehicle.The prior art approach to overcome this limitation has been to usegreater wall thicknesses, or to use more costly materials.Alternatively, if greater weight and/or cost are not tolerable, then theprior art approach is to permit higher stresses, which can negativelyimpact the performance and/or operating life of the cradle.

The process that is described above may be repeated as desired so as toproduce additional half-cradles 12 a. Of course, FIGS. 3 a-c depict themanufacture of only the first half cradle 12 a. It should be noted thatsubstantially the same process is used to manufacture the secondhalf-cradle 12 b.

Referring now to FIGS. 4 a and 4 b, optionally an end feature 36 isprovided at the ends 24 a and 24 b of the stubs 20 a and 20 b, aroundwhich ends the end member 18 is cast. For example, the end feature 36shown in FIG. 4 a is a flange that extends radially outwardly from thewall of the stubs 20 a and 20 b. As another example, the end feature 36shown in FIG. 4 b is an “anchor,” wherein the diameter of the stubs 20 aand 20 b reduces and then extends out at a 90° flange at the joint.

Referring to FIG. 4 c, optionally a slot or hole 40 is provided at theends 24 a and 24 b of the stubs 20 a and 20 b, respectively, aroundwhich ends the end member 18 is cast. When the slot or hole 40 isprovided through the wall material proximate the ends 24 a and 24 b ofthe stubs 20 a and 20 b, respectively, the molten first material is ableto flow around the inner and outer surface of the ends 24 a and 24 b andthrough the slot or hole 40, thereby forming a “pin” structure that isintegral with the end member 18. The formed “pin” structure preventsboth longitudinal and rotational movement of the cast end member 18relative to the stubs 20 a and 20 b.

Referring to FIG. 4 d, optionally a slot or hole 42 with a hanging slug44 is provided at the ends 24 a and 24 b of the stubs 20 a and 20 b,respectively, around which ends the end member 18 is cast. When the slotor hole 42 with the hanging slug 44 is provided through the wallmaterial proximate the ends 24 a and 24 b of the stubs 20 a and 20 b,respectively, the molten first material flows around the inner and outersurface of the ends 24 a and 24 b and through the slot or hole 40,thereby forming a “pin” structure that is integral with the end member18. The formed “pin” structure prevents both longitudinal and rotationalmovement of the cast end member 18 relative to the stubs 20 a and 20 b.In addition, the hanging slug 44 provides an additional anti-rotationfeature, thereby further reinforcing the bi-metallic joint.

Reference is now made to FIG. 5, which shows an exploded view of thecradle 10 of FIG. 1. The cross-members 14 a and 14 b may be formed anysuitable way. For example, one or both cross-members 14 a and 14 b aremade from a plurality of cross-member pieces. In the embodiment shown inFIG. 5, the first cross-member 14 a is made from first and secondcross-member pieces 36 a and 36 b, and the second cross-member 14 b ismade from first and second cross-member pieces 38 a and 38 b. Thecross-member pieces 36 a and 36 b may be joined together (e.g., afusion, mechanical or chemical joining, such as for instance one ofwelding, bolting, riveting, using an adhesive, etc.), and may be joined(e.g., a fusion, mechanical or chemical joining, such as for instanceone of welding, bolting, riveting, using an adhesive, etc.) to the stub20 a on the half-cradle 12 a and to the stub 20 a on the half-cradle 12b. Similarly, the cross-member pieces 38 a and 38 b may be joined (e.g.,a fusion, mechanical or chemical joining, such as for instance one ofwelding, bolting, riveting, using an adhesive, etc.) together and may bejoined (e.g., a fusion, mechanical or chemical joining, such as forinstance one of welding, bolting, riveting, using an adhesive, etc.) tothe stub 20 b on the half-cradle 12 a and to the stub 20 b on thehalf-cradle 12 b. The cross-member pieces 36 a and 36 b, and the crossmember pieces 38 a and 38 b, may be made by any suitable means, such asfor instance by stamping or by roll forming Stamping a cross-member fromsheet metal may be preferable to manufacturing a cross-member from atubular blank for several reasons, including, for example, manufacturingcost, improved design flexibility etc. Optionally, the cross-members 14a and/or 14 b are formed using a traditional hydroforming process.

Because the cores 28 a and 28 b are used to seal against leakage ofmolten first material 33 during the casting process, the cross-members14 a and 14 b need not be welded to the stubs 20 using continuous welds.In other words, the welds themselves are not needed to seal againstleakage.

It will be noted that when casting end members around cross-members withend caps in prior art cradles, the pressure imbalance between the moltenfirst material 33 in the mold cavity 26 and the interior of thecross-member urges the cross-member to move outwardly, unless thecross-member happens to have a shape that locks it in place against thepressure imbalance. Specialized locking mechanisms are otherwise neededto hold the cross-member in place against the pressure imbalance. Suchmechanisms may be difficult to provide for some cross-members that havea shape that does not lend itself easily to being held against thepressure imbalance. By providing the stubs 20 a and 20 b with thesealing shoulders 32 a and 32 b, respectively, the cores 38 a and 38 bcan hold the stubs 20 a and 20 b, respectively, in position against thepressure imbalance and thereby eliminate the need for the aforementionedspecialized locking mechanisms. When the sealing shoulders are absent,an interference fit between the cores 38 a and 38 b and the stubs 20 aand 20 b, respectively, holds the stubs 20 a and 20 b in place.

After the first and second half-cradles 12 a and 12 b, respectively, areformed they may be sent to a station for X-ray scanning to verify theintegrity of the cast end member 18. If the X-ray scan reveals thatthere are defects (e.g., large voids) in the end member 18 of one of thehalf-cradles, then that half-cradle can be scrapped and the otherhalf-cradle can still be used. This is in contrast to a situation wherea traditionally manufactured full-cradle is X-rayed and, when a defectis found in one of the end members, the entire full-cradle is scrapped.By forming the half-cradles 12 a and 12 b with the stubs 20 a and 20 bto provide a place for connection to the cross-members 14 a and 14 b,each end member 18 can be scanned individually and scrapped individuallyif it is found to be defective.

Furthermore, it is easier to X-ray half-cradles individually since fewerparts are present. Thus, it is less likely that the cross-members and/orthe second end member will obstruct the X-ray scanning machine fromhaving a clear view through the cast end member that is being X-rayed.

The half-cradles 12 a and 12 b may also be transported to other stationsduring the manufacturing process, for operations such as cleaning andaging/heat treatment, etc. Additionally, the half-cradles 12 a and 12 bmay be transferred to and stored in buffer zones during themanufacturing processing between different processing steps.Transporting and handling the half-cradles 12 a and 12 b is relativelyeasier (particularly in situations where they are handled manually by anoperator) due to their relative lightness compared to a full cradle.Additionally, storage of half-cradles 12 a and 12 b takes up less spacethan storage of full cradles, as there is relatively little open spacein the footprint of a half-cradle, whereas there is a significant amountof open space in the footprint of a full cradle (e.g., the open spacewithin the rectangle that is formed by the end members andcross-members).

Manufacturing half-cradles 12 a and 12 b using stubs 20 a and 20 b canbe carried out on smaller presses than is possible when manufacturingfull cradles, where both end members are formed simultaneously.Furthermore, the smaller presses use a one-shot tip and have simplifiedmetal delivery to the mold cavity (which may be referred to as thecrucible) as compared to the presses used to manufacture full cradles.Furthermore, the robots and mold plates associated with the smallerpresses may carry out movements more quickly than is possible on largerpresses for full cradles.

In addition, the half-cradles 12 a and 12 b can undergo a T6 treatmentwithout creating gaps at the joints between the stubs 20 a and 20 b andthe end member 18. A T6 treatment involves solution heat-treating thehalf-cradle and then artificially aging it to modify the properties ofthe aluminum. On the other hand, in some traditionally manufactured fullcradles, a T6 treatment results in loose joints between thecross-members and the end members. It is theorized that the likelihoodof improved joint integrity in the half-cradles 12 a and 12 b isprovided at least in part by the elimination of the end caps that areused in the prior art full cradle manufacture.

At stations where a machining step is carried out, in some situations itmay be possible to carry out the machining on the half-cradles 12 a and12 b prior to joining the cross-members 14 a and 14 b to them. In suchsituations, the machines that carry out the machining may be smaller forhandling the half-cradle 12 a and 12 b than they would otherwise have tobe for handling a full cradle.

Prior to connection to the half-cradles 12 a and 12 b, the cross-members14 a and 14 b in some embodiments of the instant invention receive ane-coating, wherein they are dipped in a vessel containing a coating, andare electrified to promote adhesion of the coating to their surface.After removal from the vessel containing the coating, the cross-members14 a and 14 b are emptied of any excess coating that remains capturedinside. In prior art cross-members, where end caps are provided at thetwo ends, the end caps create aperture-less end sections that caninterfere with the e-coating process in several ways. One problem withthe presence of the aperture-less end sections is that if thecross-member is immersed in the coating in certain orientations, it ispossible to wind up with an air pocket trapped at one of the endsections, which can prevent the end section from being coated. Anotherproblem with the end sections is that when the cross-member is removedfrom the vessel containing the coating, it may be difficult to drain theexcess coating from the end sections of the cross-member.

By providing cross-members 14 a and 14 b without end caps theaforementioned problems are mitigated. Providing open (i.e., uncapped)ends at each end of the cross-members 14 a and 14 b substantiallyprevents the potential for air pockets to become trapped at one of theends. Additionally, the open ends facilitate the drainage of any excesscoating.

Finite element analysis results for the end members of a prior artcradle and of a cradle made in accordance with an embodiment of thepresent invention, and for the cross-members of a prior art cradle andof a cradle made in accordance with an embodiment of the presentinvention, indicate that the cradle 10 has a lower stress profile thanthe prior art cradle with which it was compared in the stress analysis.Furthermore, a weight savings was achieved with the cradle 10 relativeto the prior art cradle.

While the cradle 10 that is shown in FIGS. 1-5 is a rear cradle, it willbe understood that the concept of providing half-cradles with stubs andwith no end caps (or with relatively thin end caps) may also be appliedto a front cradle for a vehicle.

Described above are examples of bi-metallic joints as used in a cradlefor a vehicle. It will be understood that the bi-metallic jointscontemplated in this application can be used in many other applications,such as in the frame of a vehicle, on a twist axle for a vehicle, toform a control arm, to form a vehicular body door pillar (eg. anA-pillar or a B-pillar), to form an instrument panel support, to form abumper assembly, and in a variety of non-automotive and non-vehicularapplications.

Referring now to FIG. 6, shown is an exemplary torsion beam axleassembly 200 according to an embodiment of the instant invention. Theassembly 200 includes first and second end assemblies, which are shownindividually at 208 a and 208 b, respectively, and a twist beam 206. Endassembly 208 a includes a bi-metallic joint 210 a that is formed bycasting a trailing arm 202 a around one end of a twist beam stub 204 a.Similarly, end assembly 208 b includes a bi-metallic joint 210 b that isformed by casting a trailing arm 202 b around one end of a twist beamstub 204 b. In a process that is similar to the process described abovewith reference to FIGS. 3 a-c, the one end of the twist beam stub 204 ais held in a not illustrated mold having a cavity that is shaped forforming the trailing arm 202 a and the one end of the twist beam stub204 b is held in a not illustrated mold having a cavity that is shapedfor forming the trailing arm 202 b. A not illustrated core is sealinglyreceived with the twist beam stubs 204 a and 204 b, and the trailingarms 202 a and 202 b are cast around the ends of the twist beam stubs204 a and 204 b, respectively, by introducing molten casting materialinto the not illustrated molds. After the molten material has cooled andhardened, the not illustrated molds are opened and the end assemblies208 a and 208 b are released. Subsequently, opposite ends of the twistbeam 206 are inserted into the twist beam stubs 204 a and 204 b, and thetwist beam 206 is joined to the twist beam stubs 204 a and 204 b (e.g.,a fusion, mechanical or chemical joining, such as for instance one ofwelding, bolting, riveting, using an adhesive, etc.).

Referring now to FIG. 7, shown is an exemplary control arm 300 accordingto an embodiment of the instant invention. The control arm 300 includesfirst and second tubular connector members 302 and 304, and cast members306, 308 and 310. The cast member 306 is cast about one end of a stubmember 312, the cast member 308 is cast about one end of each of stubmembers 314 and 316, and the cast member 310 is cast about one end ofstub member 318. In particular, a removable core is sealingly receivedwithin the stub member 312 when cast member 306 is cast about the oneend thereof, a removable core is sealingly received within each one ofthe stub members 314 and 316 when the cast member 310 is cast about therespective one ends thereof, and a removable core is sealingly receivedwithin the stub member 318 when cast member 310 is cast about the oneend thereof. Opposite ends of the tubular connector member 302 areinserted into the stub members 312 and 314 and the tubular connectormember 302 is joined to the stub members 312 and 314 (e.g., a fusion,mechanical or chemical joining, such as for instance one of welding,bolting, riveting, using an adhesive, etc.). Similarly, opposite ends ofthe tubular connector member 304 are inserted into the stub members 316and 318 and the tubular connector member 304 is joined to the stubmembers 316 and 318 (e.g., a fusion, mechanical or chemical joining,such as for instance one of welding, bolting, riveting, using anadhesive, etc.).

To describe a bi-metallic joint in accordance with broader aspects ofthe instant invention, reference is now made to FIG. 8, which shows abi-metallic joint 800 between a first member 802 and a second member804. The first member 802 is cast around at least a portion of thesecond member 804. The first member 802 is made from a first material,such as for instance aluminum or alloys thereof, magnesium or alloysthereof, zinc or alloys thereof, or other similar materials. The secondmember 804 is made from a second material, such as for instance steel,aluminum or alloys thereof, copper or alloys thereof, stainless steel,etc. In particular, the melting temperature of the first material islower than or approximately equal to the melting temperature of thesecond material, thereby permitting the first member 802 to be castaround the second member 804.

To form the joint 800 a portion (e.g., an end 812) of the second member804 is positioned in a mold 806. Molten first material is introducedinto the mold cavity 808 and is solidified around the portion of thesecond member 804 in the mold cavity, as described heretofore withreference to previous embodiments of the instant invention. Inembodiments wherein the second member 804 is tubular and has an endaperture 810 at the end 812, the second member 804 may be provided withan end cap 814 that is secured to the end 812 via a weld 816, so as toprevent molten first material from escaping from the mold through theend 812. In some embodiments, wherein an end cap 814 is provided, theportion of the second member 804 in the mold cavity 808 and the end cap814 may be configured to withstand the pressures of the molten firstmaterial in the mold. In accordance with other embodiments of theinstant invention, wherein the end cap 814 and the portion of the secondmember in the mold are not sufficiently strong to be able to withstandthe pressures in the mold by themselves, a core (not illustrated in FIG.8) is inserted into the interior of the second member 804 and abuttedwith the end cap 814. In this way, the core supports the second member804 and end cap 814 to permit them to withstand the pressures in themold without deforming or without deforming significantly. In someembodiments, the end cap 814 is omitted entirely and the core isinserted into the interior of the second member 804 both to support thesecond member 804 to withstand the pressures in the mold and to sealagainst the escape of molten first material from the mold through theend 812. The core optionally extends into the mold farther than thesecond member 804 or it is positioned flush with the end of the secondmember 804, or the second member 804 extends into the mold farther thanthe core. In accordance with the embodiment in which the core extendsinto the mold farther than the second member, a more lightweightbi-metallic joint may be formed, since less of the first material isrequired to form the bi-metallic joint.

The second member 804 is for instance a stub member for being connectedto another member. For example, a cradle may be fabricated with one ormore second members that are stubs that are embedded partially in a castend member (as shown in FIG. 2). Cross-members, which are made from acompatible material to the stubs, can then be welded to the stubs. Forgreater certainty, in embodiments wherein a cast first member has aplurality of second members partially embedded therein, it is notnecessary that all of the second members be made from the same material.

In one embodiment, the second member 804 is provided with featuresthereon for preventing slippage and/or rotation between the first andsecond members during use of the joint. For example, the second member804 is generally rectangular in cross-sectional shape (as shown in FIG.2) to prevent rotation of the first member and second member relative toeach other about an axis along the length of the second member. Asanother example, the second member has a flange portion thereon toprevent the first and second members from being pulled apart by forcesacting on the bi-metallic joint. Anchor and/or anti-rotation features,such as for instance a flange, slots, holes, or slots/holes with hangingflaps of punched out second material optionally are provided proximatethe end 812 about which the first member 802 is cast. When end cap 814is provided at the end 812, optionally the end cap is polygonal, such asfor instance hexagonal or octagonal, so as to prevent relative rotationbetween the first member 802 and the second member 804.

Of course, the bi-metallic joint may be used in a number ofapplications, such as on a twist beam axle assembly that includes atrailing arm and a twist beam, wherein the trailing arm is a firstmaterial such as cast aluminum and the twist beam is a second materialsuch as steel, or on a cradle, such as a rear suspension cradle or anengine cradle wherein the end members are made from cast aluminum andany cross-beams are made from a first material, such as steel. Otherapplications for such bi-metallic joints include instrument panelsupport structures, automotive frames, automotive sub-frames, crossmember rails, door beams and bumper assemblies.

After the bi-metallic joint is formed, a cross member (not shown) can beeasily joined to the second member 804. Cross members can be tubes ofvarious profiles, stampings and/or roll forms. Advantageously, the crossmembers can be designed from half shell members that are fastened toeach other. In accordance with another advantageous embodiment of theinvention, the welding of the cross member to the second member 804 doesnot have to be a full sealing weld.

While the above description constitutes a plurality of embodiments ofthe present invention, it will be appreciated that the present inventionis susceptible to further modification and change without departing fromthe fair meaning of the accompanying claims.

1. A bi-metallic component, comprising: a cast member formed from a first material; and a tubular stub member formed from a second material and having an open first end and an open second end that is opposite the first end, the cast member cast around the second end, and the first end extending from the cast member, the stub member having an interior surface that is configured to sealingly receive a removable core member for preventing molten first material from flowing through the stub member between the second end and the first end thereof during casting of the cast member around the second end.
 2. The bi-metallic component according to claim 1, wherein the first material is an aluminum alloy and the second material is steel.
 3. The bi-metallic component according to claim 1, wherein the first material has a melting temperature that is lower than or equal to the melting temperature of the second material.
 4. The bi-metallic component according to claim 1, wherein the interior surface of the stub member comprises a stub-associated sealing shoulder configured for engaging a core-associated sealing shoulder of the removable core member when the removable core member is sealingly received within the stub member.
 5. The bi-metallic component according to claim 1, wherein the interior surface of the stub member is dimensioned to receive the removable core member with a slip fit tolerance defining a gap therebetween, and wherein the second end of the stub member is sufficiently ductile so as to deform when the second end of the stub member is held in a mold during forming of the cast member around the second end, such that the width of the gap is decreased within a first region thereof, for substantially preventing molten first material from flowing between a second region on one side of the first region and a third region on a side of the first region that is opposite the one side.
 6. The bi-metallic component according to claim 1, comprising an end cap secured to the second end for sealing the open second end, at least one of the end cap and the second end of the tubular stub member having a strength that is insufficient to withstand a pressure exerted by the molten first material during casting of the cast member.
 7. The bi-metallic component according to claim 1, wherein the stub member has a cross-sectional shape that is other than circular.
 8. The bi-metallic component according to claim 1, wherein the stub member has a cross-sectional shape that is one of generally hexagonal, generally octagonal, generally square, generally rectangular, generally oval-shaped and generally L-shaped.
 9. The bi-metallic component according to claim 1, wherein the stub member has a cross-sectional shape that has a width and a height, the height larger than the width.
 10. The bi-metallic component according to claim 1, wherein the bi-metallic component is a half-cradle for use in a cradle in a vehicle frame, the cast member is a cast end member, and the tubular stub member is a first cross-member stub member.
 11. The bi-metallic component according to claim 10, comprising a second cross-member stub member formed from the second material and having a first end and a second end that is opposite the first end, the cast member cast around the second end of the second cross-member stub member, and the first end of the second cross-member stub member extending from the cast member, the second cross-member stub member having an interior surface that is configured to sealingly receive a removable core member for preventing molten first material from flowing through the second cross-member stub member between the second end and the first end thereof during casting of the cast member around the second end.
 12. The bi-metallic component according to any one of claim 1, wherein the bi-metallic component is a torsion beam axle assembly, the cast member is a cast trailing arm and the tubular stub member is a torsion beam stub member.
 13. The bi-metallic component according to claim 1, wherein the bi-metallic component is a control arm, the cast member is a cast coupling member and the tubular stub member is a steel member stub member.
 14. The bi-metallic component according to claim 1, wherein the bi-metallic component is one of an instrument panel support and a bumper assembly.
 15. A half cradle for use in a cradle in a vehicle frame, comprising: a cast end member formed from a first material; and first and second tubular cross-member stubs, each formed from a second material and each having a first end and a second end that is opposite the first end, the cast member cast around the second end of each of the first and second tubular cross-member stubs, and the first end of each of the first and second tubular cross-member stubs extending from the cast member, each of the first and second tubular cross-member stubs having an interior surface that is configured to sealingly receive a removable core member for preventing molten first material from flowing through either one of the first and second tubular cross-member stubs between a respective second end and a respective first end thereof during casting of the cast member.
 16. A torsion beam axle assembly, comprising: a cast trailing arm formed from a first material; and a torsion beam stub formed from a second material and having a first end and a second end that is opposite the first end, the cast trailing arm cast around the second end of the torsion beam stub and the first end of the torsion beam stub extending from the cast member, the torsion beam stub having an interior surface that is configured to sealingly receive a removable core member for preventing molten first material from flowing through the torsion beam stub between the second end and the first end thereof during casting of the cast trailing arm around the second end.
 17. A control arm, comprising: a cast coupling member formed from a first material; and a tubular stub member formed from a second material and having a first end and a second end that is opposite the first end, the cast coupling member cast around the second end of the tubular stub member and the first end of the tubular stub member extending from the cast coupling member, the tubular stub member having an interior surface that is configured to sealingly receive a removable core member for preventing molten first material from flowing through the tubular stub member between the second end and the first end thereof during casting of the cast coupling member around the second end.
 18. A full cradle for use in a vehicle frame, comprising: first and second half-cradles, each one of the first and second half-cradles comprising: a cast end member formed from a first material; and first and second tubular cross-member stubs formed from a second material, each of the first and second tubular cross-member stubs having an open first end and an open second end that is opposite the first end, the cast end member cast around the second end of each of the first and second tubular cross-member stubs and the first end of each of the first and second tubular cross-member stubs extending from the cast end member, each one of the first and second tubular cross-member stubs having an interior surface that is configured to sealingly receive a removable core member for preventing molten first material from flowing through either one of the first and second tubular cross-member stubs between the respective second end and the respective first end thereof during casting of the cast end member around the second end of each of the first and second tubular cross-member stubs; and a first cross-member connected between the first tubular cross-member stubs on the first and second half-cradles, and a second cross-member connected between the second tubular cross-member stubs on the first and second half-cradles, wherein the first and second cross-members are made from a material that is weldable to the second material.
 19. The full cradle according to claim 18, wherein the first material is an aluminum alloy and the second material is steel.
 20. The full cradle according to claim 18, wherein the first material has a melting temperature that is lower than or equal to the melting temperature of the second material.
 21. The full cradle according to claim 18, wherein the interior of each of the tubular cross-member stubs has a stub-associated sealing shoulder configured for sealingly receiving a core-associated sealing shoulder on each of the core members.
 22. The full cradle according to claim 18, wherein the interior surface of each of the first and second tubular cross-member stubs is dimensioned to receive the removable core members with a slip fit tolerance defining a gap there between, and wherein the second end of each of the first and second tubular cross-member stubs is sufficiently ductile so as to deform when held in a mold during forming of the cast end member around the second end, such that the width of the gap is decreased within a first region thereof, for substantially preventing molten first material from flowing between a second region on one side of the first region and a third region on a side of the first region that is opposite the one side.
 23. The full cradle according to claim 18, comprising an end cap secured to the second end of each one of the first and second tubular cross-member stubs for sealing the open second ends thereof, at least one of the end caps and the second ends of the first and second tubular cross-member stubs having a strength that is insufficient to withstand a pressure exerted by the molten first material during casting of the cast end member.
 24. The full cradle according to claim 18, wherein the first tubular cross-member stub and the first cross-member each has a cross-sectional shape that is other than circular.
 25. The full cradle according to claim 24, wherein the second tubular cross-member stub and the second cross-member each has a cross-sectional shape that is other than circular.
 26. The full cradle according to claim 24, wherein the first tubular cross-member stub and the first cross-member each has a cross-sectional shape that has a width and a height, the height larger than the width.
 27. The full cradle according to any one of claim 24, wherein the first tubular cross-member stub and the first cross-member has a cross-sectional shape that is one of generally hexagonal, generally octagonal, generally square, generally rectangular, generally oval-shaped and generally L-shaped.
 28. The full cradle according to claim 25, wherein the second tubular cross-member stub and the second cross-member each has a cross-sectional shape that has a width and a height, the height larger than the width.
 29. The full cradle according to claim 28, wherein the second tubular cross-member stub and the second cross-member each has a cross-sectional shape that is one of generally hexagonal, generally octagonal, generally square, generally rectangular, generally oval-shaped and generally L-shaped.
 30. A method of making a bi-metallic component, comprising: a) providing a first material; b) providing a tubular stub member made from a second material; c) positioning a portion of the tubular stub member in a mold; d) removably inserting a core into the tubular stub member; e) introducing the first material in molten form into the mold around the tubular stub member; f) holding the core in the tubular stub member with a sufficient force to prevent first material from filling the tubular stub member; g) solidifying the first material to form a cast member in the mold around a portion of the tubular stub member, the solidified cast member and the tubular stub member together forming the bi-metallic component; and h) opening the mold to release the bi-metallic component.
 31. The method according to claim 30, wherein the first material is an aluminum alloy and the second material is steel.
 32. The method according to claim 30, wherein the first material has a melting temperature that is lower than or equal to the melting temperature of the second material.
 33. The method according to claim 30, wherein an end of the tubular stub member is positioned in the mold during step d) and wherein the removable core extends beyond the end of the tubular stub member and into the mold.
 34. A method of making a half-cradle for use in a cradle in a vehicle frame, comprising: a) providing a first material; b) providing first and second tubular cross-member stubs made from a second material; c) positioning a portion of each of the first and second tubular cross-member stubs in a mold; d) removably inserting first and second cores into the first and second tubular cross-member stubs, respectively; e) introducing the first material in molten form into the mold around the first and second tubular cross-member stubs; f) holding the first and second cores in the first and second tubular cross-member stubs with a sufficient force to prevent first material from filling the first and second tubular cross-member stubs; g) solidifying the first material to form an end member in the mold around the portion of each of the first and second tubular cross-member stubs, the solidified end member and the first and second tubular cross-member stubs together forming a half-cradle; and h) opening the mold to release the half-cradle.
 35. The method according to claim 34, wherein the first material is an aluminum alloy and the second material is steel.
 36. The method according to claim 34, wherein the first material has a melting temperature that is lower than or equal to the melting temperature of the second material.
 37. The method according to claim 34, wherein an end of each of the first and second tubular cross-member stubs is positioned in the mold during step d) and wherein the first and second cores extend beyond the ends of the first and second tubular cross-member stubs and into the mold.
 38. A method of making a full cradle for use in a vehicle frame, comprising: a) making a first half-cradle according to the method claimed in claim 34; b) making a second half-cradle according to the method claimed in claim 34; c) connecting a first cross-member to the first tubular cross-member stub on each of the first and second half-cradles; and d) connecting a second cross-member to the second tubular cross-member stub on each of the first and second half-cradles.
 39. The method according to claim 38, wherein the first and second cross-members are made from the second material.
 40. The method according to claim 38, wherein at least one of the first and second cross-members is made from first and second cross-member portions fixedly connected one to the other.
 41. The method according to claim 38, wherein at least one of the first and second cross-members is made by: e) stamping a first cross-member portion; f) stamping a second cross-member portion; and g) connecting the first and second cross-member portions together.
 42. The method according to claim 38, comprising: h) checking the integrity of the first half-cradle prior to step c); and i) checking the integrity of the second half-cradle prior to step c).
 43. The method according to claim 42, wherein steps h) and i) comprise checking the integrity of the solidified first material.
 44. A method of making a bi-metallic joint, comprising: a) providing a first metal; b) providing a second member made from a second metal, the second member having an end aperture at an end thereof; c) sealing the end aperture with an end cap; d) inserting a core into the second member in abutment with the end and with the end cap; e) positioning the end of the second member in a mold; f) introducing the first metal in molten form into the mold around the end of the second member and the end cap; g) solidifying the first metal to form a first member in the mold around the end of the second member and the end cap; and h) removing the core from the second member, wherein the end cap and the end of the second member are not sufficiently strong to withstand a pressure in the mold during steps f) and g); and wherein the core remains in abutment with the end and with the end cap during steps f) and g) and prevents substantial deformation of either the end or the end cap during steps f) and g).
 45. A method of making a bi-metallic joint, comprising: a) providing a first metal; b) providing a second member made from a second metal, the second member having an end aperture at an end thereof; c) removably inserting a core into the second member through an open first end thereof, the core configured for substantially forming a seal, during a molding process, between an outer surface thereof and an interior surface of the second member that faces the outer surface of the core; d) positioning an open second end of the second member in a mold, the second open end opposite the first open end; e) introducing the first metal in molten form into the mold around the second open end of the second member; f) solidifying the first metal to form a first member in the mold around the second open end of the second member; and g) removing the core from the second member. 